APA (7th ed.) Citation

Petrides, G. A., & Petrides, O. (1992). A field guide to western trees: Western United States and Canada. Houghton Mifflin Co..

Chicago Style (17th ed.) Citation

Petrides, George A., and Olivia Petrides. A Field Guide to Western Trees: Western United States and Canada. Boston: Houghton Mifflin Co., 1992.

MLA (9th ed.) Citation

Petrides, George A., and Olivia Petrides. A Field Guide to Western Trees: Western United States and Canada. Houghton Mifflin Co., 1992.